Automatic fire alarm device

ABSTRACT

Automatic fire alarm incorporating a device for detection of combustion gases comprising a detection cell having a cathode, an anode accessible to the combustion gases and an electrolyte arranged between the anode and cathode. The anode catalytically oxidizes the carbon monoxide contained in the combustion gases while giving off electrons. An electrical circuit is coupled with the anode and the cathode for current detection and alarm indicating purposes.

States Patent 1191 111] 3,7553% Purt et al. 1 Aug. 28, 1973 [54}AUTOMATIC FIRE ALARM DEVICE 2,508,588 5/1950 Waltman 340/237 R X3,237,181 2/l966 Palmer [75] lnvenmrs g t i lig ig iz d 3,479,25711/1969 Shaver 340/237 R ux e r, aa, 0 0 WI eran [73 Assignee: CerberusMannedorf Primary Examiner-John W. Caldwell Sw'tzefland AssistantExaminer-Daniel Myer 22 Filed; July 10 1972 Attorney-Werner W. Kleeman[2]] Appl. No.: 270,479

[57] ABSTRACT [30] Foreign Application Priority Data Jul 15 1971Switzerland 1043?]71 Automatic fire alarm incorporating a device fordetecy tion of combustion gases comprising a detection cell having acathode, an anode accessible to the combus- Ff'i 340/237 23/254 i tiongases and an electrolyte arranged between the [58] Fieid 23/254 E anodeand cathode. The anode catalytically oxidizes 23/255 the carbon monoxidecontained in the combustion gases while giving off electrons. Anelectrical circuit is 5 6] References Cited coupled with the anode andthe cathode for current detection and alarm indicating purposes. UNITEDSTATES PATENTS 2,114,401 4/1938 Price 340/237 R 21 Claims, 3 DrawingFigures ower Su l PATENTEDwcza ms 3; 755800 \2e 2 Cathode 5 I I I I \Z 2Cathode 1 5 7 I! 1 1] 1111/11/11 2H +26 u 1 1 I I l q] 4//' I .1 '1" 2H+I (H3 Alarm 1 noe 2 I TA: Fig.2

(Air) Alarm ower Smppl Fig.3

1 AUTOMATIC FIRE ALARM DEVICE BACKGROUND OF THE INVENTION The presentinvention relates to a new and improved construction of automatic firealarm incorporating a device for the detection of combustion gases.

Automatic fire alarms either resort to the use of the physical changesarising during a combustion process, for instance the increase intemperature or the radiation transmitted by flames for the purpose ofindicating an alarm, or attempt to detect the products of combustionresulting during a fire. Hence, it is known in this particular field oftechnology to detect the smoke which develops during combustionprocesses by optical absorptionor stray light fire alarm devices or todetect the combustion aerosols by means of ionization fire alarms. Otherstate-of-the-art fire alarm devices resort to the use of the changedconductivity of the combustion gases (formation of ions) and theincreased water vapor content for fire detection purposes.

However, the aforementioned equipment is more or less subject todisturbances that can be triggered by occurrences which have nothingtodo with a combustion process, for instance in the case of optical firealarms by disturbing light effects, in the case of ionization firealarms by dust, in the case of conductivity detectors by the ionizationof air or for other causes. Due to such deception of the relevant firedetection devices in the aforementioned manner false alarms arise withSue prior art equipment.

It has already been proposed to employ for fire detection purposes thecarbon monoxide (CO) which is-produced during any undesired orintentional combustion process. Such type equipment would operate in apar ticular foolproof manner since carbon monoxide occurs practicallyexclusively as a result of a combustion process, and therefore,constitutes an infallible indicator for a fire. Moreover, a warningconcerning the presence of carbon monoxide is extremely desirable owingto the fact that it is poisonous.

Heretofore known CO-detectors generally function on thespectral-photometric principle or by means of a chemical reaction andthe detection of the resultant products. However, these procedures arerelatively cumbersome and the equipment operated in accordance therewithis not useable over longer periods of time, as such is required forautomatic fire alarms- Additionally, such type equipment is relativelycomplicated, expensive and requires continuous maintenance.

SUMMARY OF THE INVENTION Hence from what has been explained above itshould be apparent that this particular field of technology is still inneed of automatic fire alarm devices which. are not associated with theaforementioned drawbacks and limitations of the state-of-the-artproposals. Therefore, it is a primary object of the present invention toprovide a new and. improved construction of automatic fire alarm devicewhich affectively and reliably fulfills the existing need in the art andovercomes the aforementioned drawbacks and limitations of the heretoforeproposed fire detection devices.

Another and more specific object of the present invention aims at theprovision of an automatic fire alarm device which overcomes theaforementionedv drawbacks and functions with increased sensitivity andin an unmistakable operationally reliable manner over longer periods oftime.

Yet a further significant object of the present invention relates toanimproved automatic fire alarm which is relatively simple inconstruction, economical to manufacture, extremely reliable inoperation, and requires minimum servicing and mainenance.

Now in order to implement these and still further objects of theinvention, which will become more readily apparent as the descriptionproceeds, the inventive apparatus for the detection of combustion gasesembodies an electrolytic cell. having a cathode, an anode accessible tothe combustion gases and an electrolyte arranged between the anode andcathode. The anode is capable of catalytically oxidizing the carbonmonoxide contained in the combustion gases while giving off electrons.There is also provided an electrical circuit connected with the anodeand cathode for current detection and alarm indicating purposes.

The invention resorts to the use of the well known experience that it ispossible by means of so-called fuel cells to directly convertcombustible liquids or gases, that is without interposing thermalengines, into electrical energy. In such type fuel cells generallyorganic substances, such as formal, formic acid or hydrazine arecatalytically oxidized, for instance at a platinum anode. Between theanode and the cathode there thusprevails a potential difference whichcan be employedv for generating energy. It has already been proposed toinversely employ the energy supply of such fuel cells for the analysisof the content of combustible material in liquids and gases. However,the known fuel cells are completely unsuitable as fire detectors owingto their complicated construction and low selective sensitivityto-carbon monoxide. Hence, in order to develop the invention it wastherefore necessary to find new materials for the individual elementsand to arrive at and select an arrangement and construction designedsuch that the apparatus possessed optimum sensitivity to carbon monoxidewith as little as possible expenditure in equipment and with as great aspossible equipment life.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be betterunderstood and objects other than those set forth above, will becomeapparent when consideration is given to the following detaileddescription above. Such description makes reference to annexed drawingswherein:

FIG. 1 schematically illustrates the functional principles of a tirealarm device employing a basic electrolyte;

FIG. 2 schematically illustrates the functional principles of a firealarm: device employing an acidic electrolyte; and

FIG. 3 illustrates in sectional view the construction of the detection.device of a. fire alarm designed according to the teachings of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Considering now'thedrawing in the embodiment of exemplary apparatus depicted in FIG. 1 theambient air has access to an anode 1. At the cathode 2 reactive oxygen.ions are formed from the oxygen molecules of the air upon delivery ofelectrons from the electrical circuit 3. These reactive oxygen ionstogether with the water of the basic electrolyte 4 are converted intohydroxyl ions. Hence, the cathode 2 serves as hydroxyl-ion donor. Thesehydroxyl ions migrate to the anode 1 and at that location react in thepresence ofa catalyst, for instance palladium, with the carbon monoxidecontained in the air into carbonic acid and water, wherein electrons arereleased which are again supplied to the electrical current circuit 3.As long as carbon monoxide is contained in the air a current flow willbe maintained in this current circuit 3, and this current flow can beascertained by means of a suitable detector and employed for triggeringan alarm signal in known manner.

Now, with the equipment depicted in FIG. 2 employing an acidic, in otherwords an electrolyte containing hydrogen ions, the carbon monoxidecontained in the air catalytically reacts at the anode l with the watercontained in the electrolyte to form carbon dioxide and hydrogen ionswhile giving off electrons which can flow in the electrical currentcircuit 3 to the cathode 2. The hydrogen ions are absorbed or taken upby the acidic electrolyte 4 and react at the cathode 2 with the oxygenwhich has diffused-in to form water while taking-up electrons from thecurrent circuit 3. The electrolyte may contain in this instancephosphoric acid.

Now in FIG. 3 there is illustrated in sectional view a practicalexemplary embodiment of the invention. Here the automatic fire alarm orfire detection device comprises a plastic housing H formed of twohousing portions or components 6 and 7, the housing portion 7 beingprovided with an opening or otherwise suitably designed so as to haveone side thereof accessible to the surrounding air. At this open side ofthe housing there is arranged a gas pervious membrane or diaphragm 8,for instance a filter formed of pressed glass wool or glass frit or thelike.

At the outside of this gas permeable membrane 8 there is provided alayer 9 formed of nickel powder coated with a noble or precious metal.Particularly suitable for this purpose are metals of the platinum group.In particular palladium has been found to possess advantageouscapabilities for the catalytic oxidation of the carbon monoxide arrivingat the diaphragm or membrane 8. The metal powder is mixed with an ionexchanger and if necessary with an additional binder, for instancepolystyrene. Basically ion exchangers of .the most different compositionhave been found to provide favorable results. Particularly suitable asthe ion exchanger is the known ion exchanger available on the marketunder the designation anion exchanger III, which contains a copolymer ofstyrene divinylbenzoyl with quaternary ammonium groups. However, theinvention is in no way to be considered limited to such type ionexchanger since other ion exhangers have been likewise found to besuitable.

At the floor of the housing portion 6 there is located an electrode 12which is coated at the inside with a layer of 'carbon, for instancecarbon black, at which there is again applied a substance 1 1 whichgives off bydroxyl ions. Particularly suitable for this purpose is apolymeric phtalocyanine of the transition metals, for instance the irongroup (Fe, Ni, Co), yet also ofCu, Ag, Au and Hg.

Now, between the plate-shaped constructed electrodes there is located athin felt layer imbued with an electrolyte, for instance a potassiumbicarbonate soslightly hinders the diffusion, as such is known forinstance from electrolytic dry elements. The layer thickness amounts toonly a few millimeters, as a rule less than 5 millimeters. With suchsubstantially plateshaped electrode arrangement and such slightelectrode spacing, i.e., less than 5 millimeters, the internalresistance of the electrolytic cell is relatively small and thediffusion within the electrolyte is sufficiently rapid so that thecurrent yield is sufficiently large so as to be already able to detectthe slightest quantities of combustion gas. The voltage of the elementin this case as a general rule is below 0.1 volts.

In order to reduce rate of evaporation or vaporization of theelectrolyte there can be added thereto a certain quantity of gylcerineor a similar substance. in this way the life and useful time of the firealarm can be considerably improved.

A further possibility of reducing evaporation of the electrolyte residesin designing the anode such that the outer side or face contains ahydrophobic binder such as indicated as 9a which prevents the escape ofthe electrolyte, whereas the inside or inner face 9b contains ahydrophylic binder which ensures for the requisite wetting or imbuing.

The sensitivity can be further increased in that the rear wall of thehousing portion 6 bearing against the cathode 12 is designed to bepervious to air. In this way the oxygen of the air can arrive directlyat the cathode 12 without having to diffuse through the electrolyte, forinstance the cathode can be formed of very finely divided silver,so-called Raney silver, which is applied to an oxygen pervious membrane.At the anode there is connected a current conductor 13 and at thecathode a current conductor 14 in order to be able to couple the firealarm device with the electrical circuit 3 serving for current detectionand alarm sounding purposes. The invention is not limited to anyspecific construction of the current detector and alarm soundingcircuitry since many different constructional forms suitable for thispurpose are wellknown in the art. In one very simple manifestation thiselectric circuit 3 can embody a relay 20 electrically coupled with thecurrent conductors 13 and 14 as shown in FIG. 3, the relay 20cooperating with a work contact 22, so that upon current flow throughthe relay 20 the work contact 22 is closed and a suitable alarm 24 isactivated since it is now placed in circuit with a suitable powersupply, such as battery 26.

It has been found that by observing the described measures it ispossible to produce a fire alarm which is capable of already positivelydetecting a carbon monoxide content below 100 ppm and which will not benormally excited into a state of producing a false alarm by contaminantsin the air.

While there is shown and described present preferred embodiments of theinvention, it is to be distinctly understood that the invention is notlimited thereto but may be otherwise variously embodied and practisedlution or cesium carbonate solution. instead of using felt it would bepossible to employ a different carrier material which can absorb theelectrolyte, yet only within the scope of the following claims. ACCORD-INGLY,

What is claimed is:

1. An automatic fire alarm comprising a device for the detection ofcombustion gases, said device comprising a detection cell having acathode, an anode accessible to the combustion gases, and an electrolytearranged between the anode and cathode, said anode being capable ofcatalytically oxidizing carbon monoxide contained in combustion gaseswhile giving ofi electrons, and an electrical circuit for currentdetection and indicating an alarm electrically coupled with said anodeand said cathode.

2. The automatic fire alarm as defined in claim 1, wherein saidelectrolyte possesses basic properties and said cathode is formed ofmaterial capable of delivering hydroxyl ions.

3. The automatic fire alarm as defined in claim 1, wherein theelectrolyte possesses acidic properties and said cathode is formed of amaterial capable of takingup hydrogen ions.

4. The automatic fire alarm as defined in claim 1, wherein the cathodepossesses a polymeric phtalocyanine of a transition metal.

5. The automatic fire alarm as defined in claim 4, wherein said cathodecontains carbon black coated with a phtalocyanine of the iron group.

6. The automatic fire alarm as defined in claim 1, wherein the anodecontains a catalyst selected from a metal of the platinum group.

7. The automatic fire alarm as defined in claim 6, wherein the anodecontains as the catalyst palladium.

8. The automatic fire alarm as defined in claim 6, wherein the anodecontains nickel powder coated with a metal of the platinum group.

9. The automatic fire alarm as defined in claim 8, wherein the nickelpowder is applied to a gas permeable membrane.

10. The automatic fire alarm as defined in claim 2, wherein the anodecontains an ion exchanger.

11. The automatic fire alarm as defined in claim 10, wherein the ionexchanger comprises a copolymer of styrene divinybenzyl with quaternaryammonium groups.

12. The automatic fire alarm as definedin claim 2, wherein theelectrolyte contains potassium bicarbonate.

13. The automatic fire alarm as defined in claim 2, wherein theelectrolyte contains cesium carbonate.

14. The automatic fire alarm as defined in claim 3, wherein theelectrolyte contains phosphoric acid.

15. The automatic fire alarm as defined in claim 1, further including aporous layer arranged between the anode and cathode and imbued with theelectrolyte.

16. The automatic fire alarm as defined in claim I, wherein theelectrolyte has added thereto an evaporation-retarding substance.

17. The automatic fire alarm as defined in claim 16, wherein theevaporation-retarding substance is glycerme.

18. The automatic fire alarm as defined in claim I, wherein said anodeand cathode possesses a substantially plate-shaped configuration and arearranged at a spacing from one another which is less than 5 millimeters.

19. The automatic fire alarm as defined in claim I, wherein both theanode and cathode are designed to be accessible to the ambient air.

20. The automatic fire alarm as defined in claim 19, wherein saidcathode is formed of very finely divided silver applied to an oxygenpervious membrane.

21. The automatic fire alarm as defined in claim 1, wherein said anodepossesses at the side thereof confronting the electrolyte a hydrophilicsubstance and at the outside a hydrophobic substance.

2. The automatic fire alarm as defined in claim 1, wherein saidelectrolyte possesses basic properties and said cathode is formed ofmaterial capable of delivering hydroxyl ions.
 3. The automatic firealarm as defined in claim 1, wherein the electrolyte possesses acidicproperties and said cathode is formed of a material capable of taking-uphydrogen ions.
 4. The automatic fire alarm as defined in claim 1,wherein the cathode possesses a polymeric phtalocyanine of a transitionmetal.
 5. The automatic fire alarm as defined in claim 4, wherein saidcathode contains carbon black coated with a phtalocyanine of the irongroup.
 6. The automatic fire alarm as defined in claim 1, wherein theanode contains a catalyst selected from a metal of the platinum group.7. The automatic fire alarm as defined in claim 6, wherein the anodecontains as the catalyst palladium.
 8. The automatic fire alarm asdefined in claim 6, wherein the anode contains nickel powder coated witha metal of the platinum group.
 9. The automatic fire alarm as defined inclaim 8, wherein the nickel powder is applied to a gas permeablemembrane.
 10. The automatic fire alarm as defined in claim 2, whereinthe anode contains an ion exchanger.
 11. The automatic fiRe alarm asdefined in claim 10, wherein the ion exchanger comprises a copolymer ofstyrene divinybenzyl with quaternary ammonium groups.
 12. The automaticfire alarm as defined in claim 2, wherein the electrolyte containspotassium bicarbonate.
 13. The automatic fire alarm as defined in claim2, wherein the electrolyte contains cesium carbonate.
 14. The automaticfire alarm as defined in claim 3, wherein the electrolyte containsphosphoric acid.
 15. The automatic fire alarm as defined in claim 1,further including a porous layer arranged between the anode and cathodeand imbued with the electrolyte.
 16. The automatic fire alarm as definedin claim 1, wherein the electrolyte has added thereto anevaporation-retarding substance.
 17. The automatic fire alarm as definedin claim 16, wherein the evaporation-retarding substance is glycerine.18. The automatic fire alarm as defined in claim 1, wherein said anodeand cathode possesses a substantially plate-shaped configuration and arearranged at a spacing from one another which is less than 5 millimeters.19. The automatic fire alarm as defined in claim 1, wherein both theanode and cathode are designed to be accessible to the ambient air. 20.The automatic fire alarm as defined in claim 19, wherein said cathode isformed of very finely divided silver applied to an oxygen perviousmembrane.
 21. The automatic fire alarm as defined in claim 1, whereinsaid anode possesses at the side thereof confronting the electrolyte ahydrophilic substance and at the outside a hydrophobic substance.